We propose to quantitate, by dual photon absorptiometry and computed tomography of the lumbar spine, the axial integral and trabecular mineral content in male patients with primary and pituitary hypogonadism, and in patients of both sexes who have had thyroid disease of have hyperparathyroidism. The application of these sensitive techniques, in conjunction with the appraisal of integral appendicular bone mineral content and appropriate endocrine testing, shall permit the critical appraisal of skeletal integrity in these important endocrine disorders prior to clinically overt bone disease. Initial cross-sectional studies of patients and their controls shall include historical, physical examination and biochemical screening for other recognized disorders leading to bone loss, and attempts to correlate axial bone mineral content with age, duration of endocrinopathy, hormone measurements, fasting urinary excretion of calcium and hydroxyproline, and hand radiogrammetry. Once baseline measurements are made, serial (annual) analyses of spinal mineral content shall be performed in control subjects and patients to assess the changes associated with their management. Our studies should provide new and clinically important information concerning appendicular and axial skeletal mineral content in (1) primarily and secondarily hypogonadal males without and with therapy with testosterone replacement. (2) spontaneous and iatrogenic disorders of the thyroid, including patients on replacement thyroxine, but not calcitonin; (3) hyperparathyroid patients before and after surgery or during long- term "medical" management. Our proposal addresses clinically important questions, and the data should characterize bone mineral content and its change during currently accepted management of these endocrine disorders. Clearly, the results could influence the diagnosis, prognosis and management of these conditions.